A seat/backrest construction incorporating a gas spring is known from U.S. Pat. No. 2,018,825. The gas spring is arranged in a fixed (but selectable) position, and serves to provide added comfort to a user.
In order to cater for persons of various weight and strength the gas spring is selected from a range of gas springs each with a fixed rating. In case of a disabled child who is still growing the gas spring may have to be replaced frequently during the life of the wheelchair, because the forces applied to the backrest increases as the weight and height of the child increase. Therefore a certain size of gas spring (a certain tension) will only be optimally suited for the seat for a limited period of time.
It would therefore be advantageous to provide a seat for a wheelchair that is suited for disabled children who are still growing.